Patricia Bosworth, an actress-turned-writer whose biographies of fellow Actors Studio alumni Montgomery Clift, Marlon Brando and Jane Fonda were best-sellers and, certainly with the Clift book, definitive for their times, died Thursday of complications related to COVID-19. She was 86.

Bosworth’s stepdaughter Fia Hatsav told The New York Times that the author died of pneumonia brought on by the coronavirus.

Bosworth began her show business career as a model in the 1950s (she was photographed by Diane Arbus, whose life she’d later chronicle) before enrolling in New York’s Actors Studio to study with Lee Strasberg. Classmates included Brando and Marilyn Monroe. She appeared on Broadway in, among other productions, Inherit the Wind, and through the 1950s and ’60s on such TV shows as Kraft Theatre, Naked City and The Patty Duke Show. Her major film credit was 1959’s The Nun’s Story.

She pivoted to a journalism career in the 1960s, writing or editing over the years for publications including New York Magazine, McCalls, Harper’s Bazaar, The New York Times, Mirabella and, in the 1980s, Vanity Fair.

Bosworth found perhaps her truest calling with the 1978 publication of Montgomery Clift: A Biography, a book that remains a go-to account of the actor’s life. Diane Arbus followed in 1984, Marlon Brando in 2000 and Jane Fonda: The Private Life of a Public Woman in 2011. The Arbus book was later adapted for the 2006 film Fur starring Nicole Kidman.

The author also wrote the memoirs Anything Your Little Heart Desires: An American Family Story, a 1997 account of her family during the Hollywood Blacklist. Her father, attorney Bartley Crum, defended clients against the House Un-American Activities Committee, and in 1959 committed suicide.

Bosworth’s second memoir was 2017’s The Men in My Life: A Memoir of Love and Art in 1950’s Manhattan. She taught literary non-fiction at Columbia University’s School of Journalism and Barnard College, and was a longtime board member of the Actors Studio.